Self-contained automatic valve tappet



D May 22, 1951 H. H. ENGEMANN SELF-CONTAINED AUTOMATIC VALVE TAPPETFiled Dec. 6, 1946 HERBERT EN EMANN' Patented May 22, 61951SELF-CONTAINED AUTOMATIC VALVE TAPPET Herbert H. Engemann, ClevelandHeights, Ohio Application December 6, 1946, Serial No. 714,491

-10 Claims. ('01. 123-90) This invention relates to self-containedautomatic adjusters for taking up clearance in a linkage assemblywithout producing an unwanted extension of the assembly.

Specifically, the invention deals with a selfcontained hydraulic valvetappet of the piston and cylinder type which is equipped with a separateshell around the cylinder and has expansible bellows anchored on theends thereof.

The valve tappets of this invention are complete in themselves and needno communication with reservoirs for hydraulic operating fluid or thelike.

According to the invention, opposed interconnected fluid-filledexpansible and contractible chambers feed a piston chamber in a cylinderwith working fluid and receive working fluid from the piston chamber.The piston is bottomed on fluid trapped in the chamber during theValveopening cycle. A check valve on the cylinder traps the fluid in thepiston chamber. Some leakage occurs from the piston chamber into one ofthe expansible chambers during the valveopening cycle, and a very slightclearance condition is thereby obtained in the valve linkage during thevalve-opening cycle. ,This clearance may be increased or decreased bywear, expansion, or contraction, but is immediately reclaimed after thevalve-closing cycle, wherein working fluid from the expansible andcontractible chambers is again admitted into the piston chamber throughthe check valve for acting on the piston to cause it to assume ano-clearance position.

A feature of the invention resides in the use of expansible andcontractible chamber-defining members secured on opposite ends of acylinder containing shell for housing the working fluid of apiston-actuated tappet without ever subjecting these chambers toforce-transmitting loads. Since these chambers are conveniently definedby metal bellows, the bellows metal is soldered or brazed to the shellwithout distorting or affecting metallurgical properties, such ashardness, of the cylinder or the piston.

Another feature of the invention resides in the formation of a passageconnecting the bellows chambers by merely creating a localized gapbetween the shell and cylinder. This gap is conveniently produced bygrinding or machining a flat band area along the length of the outerface of the cylinder.

Still another feature of the invention resides in the provision of acheck valve on the cylinder instead of on the piston of a self-containedpiston and cylinder type tappet to thereby eliminate heretofore requiredvalve-closing springs.

A further feature of the invention resides in the provision of a tappetassembly that can'be easily completely filled with working fluid topurge out heretofore-encountered air bubbles which, being compressible,cause malfunctioning of the tappet. The elimination of air from thetappet renders it useful in any position.

An object of the invention is to provide a selfcontained piston andcylinder type automatic extensible and contractible device forcontrolling clearance conditions in a linkage assembly, which device hasa separate bellows-carrying shell surrounding the cylinder thereof.

A further object of the invention is to provide a self-containedautomatic hydraulic valve tappet having expansible and contractibleworking fluid chambers which are never subjected .toforce-transmittingloads and are connected with each other through a gap between two nestedmembers.

A still further object of the invention is to provide a self -containedcylinder and piston type automatic valve tappet with opposedinterconnected liquid-filled spring bellows for feeding working fluidthrough a cylinder-mounted check valve to a piston chamber and forreceiving working fluid leaking from the piston chamber thereby causingthe piston to contract the tappet when loaded during a valve-operatingcycle, and to extend when unloaded during a valve operating cycle.

Another object of the invention is to provide a self-contained hydraulicvalve tappet with a piston acted on by liquid trapped with a springlessvalve during the valve-opening cycle and receiving additional liquidthereagainst after the valve-closing cycle for replenishing oil leakingpast the piston during the valve-opening cycle, with an amount justsufficient to cause ex tension of the tappet to a no-clearance conditionin the valve linkage.

Another object of the invention is to provide a piston and cylinder typebellows-equipped valve tappet with a floating piston free from anchoringconnections with a bellows.

A further object of the invention is to provide a self-containedhydraulic valve tappet with opposed liquid-filled intercommunicatingbellows chambers on the ends of a separate shell, a piston chamberconnected to one of said bellows chambers through a checkvalve-controlled passage, and a piston slidable freely in the chamber toallow leak-down of fluid from the piston chamber into the other bellowschamber.

Other and further objects of this invention will be apparent to thoseskilled in the art from the following detailed description of theannexed sheet of drawings which show a preferred embodiment of theinvention.

On the drawings:

Figure l is an enlarged axial cross-sectional view, with partsinelevation, of a self-contained hydraulic valve tappet according tothis invention in its free expanded condition.

Figure 2 is a view similar to Figure 1, but illustrating the tappet inits working condition in a valve train.

Figure 3 is a transverse cross sectional view taken alon the line IIIIJIof Figure 1.

Figure 4 is a framentary cross-sectional view of an alternate end caparrangement illustrating a filling of the tappet with fluid.

Figure 5 is a view similar to Figure 4, but showing the filling tube insealed condition.

As shown on the drawings:

In Figures 1 and 2 the reference numeral I I] designates generally aself-contained automatic valve tappet according to this invention. Thetappet I includes a hollow tappet body II .pro-

viding a chamber I2. The body II has a closed bottom IIa, a cylindricalside wall Ilb, a thickened rim top portion lie, and a top shoulder Md.The thickened port-ion IIIc provides a reduced-diameter bore I2a givingaccess to the chamber I2. A shell I3 is partially disposed in thechamber I2 and has a cylindrical side wall I3a snugly fitting the boreI2a together with an out-turned flange I3b bottomed on the shoulder Md.The shell I3 is hollow with open ends, and has an internal shoulder I3cintermediate said open ends. A first rim bead I3d isprovided at theupper end of the shell above the flange I3b and has anchored thereon oneend of a first springmetal bellows 14. The other end of the shell has asecond rim bead I3e having anchored thereon one end of a secondspring-metal bellows I5. To insure leak-proof joints between the shelland bellows, the bellows are soldered, brazed, or welded to the ends ofthe shell. The bellows I4 is outside of the body I I, while the bellowsI5 is disposed entirely within the chamber I2 of the body II, but infreely spaced'relation from any of the walls of the body.

A cylinder I6 is seated in the shell I3 and has a shoulder I601,bottomed on the shoulder I30 of the shell. The cylinder I5 has acylindrical bore I6b extending from the open top thereof to a slightlyenlarged chamber I60. A piston I1 is slidable in the bore I61) and hasits end face projecting into the chamber I66. The piston I! has anintegral rod portion Ila projecting above the cylinder I6, andterminating in a head I'Ib having a rounded top surface [10. The top endface of the cylinder I6 has a groove I6d therein receiving the bottomend coil of a spring I8. This spring I8 has the other end coil thereofbottomed on a shoulder provided under the head I lb of the piston,sothat the spring is effective to urge the piston outwardly of thecylinder I6. An end cap I9 overlies the piston head I11) and is adaptedto rock on the surface I'Ic thereof. This cap I9 has a bead rim I9aaround the bottom thereof receiving the top end of the bellows I! insealed engagement therewith. The cap I9 has ;a fragmental sphericalrecess I921 in its top face adapted to receive therounded lower end of apush rod P (Figure 2) in a valve train.

4 shell I3. This chamber 20 receives the piston rod Ho and the spring I8therein.

The bellows I5 in the chamber I2 of the body II is closed by an end cap2| having an internally threaded boss portion 2Ia receiving a threadedclosure plug 22. The bellows I5 thus encloses a chamber 23 on the lowerend of the shell I3 withinthe chamber I2 of the body II.

This chamber 23 is in'communication with and receives a part of thecylinder I6.

The bellows chambers 20 and 23 are joined by a, passageway 24. Thispassageway 24 is formed between the shell I3 and cylinder I6 by a flatband area "is on the outer cylindrical wall of the cylinder I6 as bestshown in Figure 3.

The bottom of the piston chamber I in the cylinder I6 has a well IS inthe central portion thereof. This well is joined, by a reduced-cliameterpassageway I 6gthrough the end of the cylinder, with the interior of thebellows chamber 23. A metal ball 25 is disposed in the well I61 andseats on the top end of the passageway IIig to close this passageway. Aninverted cup memher-26 is 'seatedin the wellIIif-around the ball 25 andhas a top WalLsubstantialIy flush with the bottom of the piston chamberI6c, equipped with a small orifice-21 to connect the piston chamber I60with the interior of the cup around the ball 25. As shown, the ball isfree to rise and fall in the cup onto and off of its seat at the top ofthe passageway I60.

In its free unloaded condition, the tappet II) assumes the extendedpositionof Figure 1 because the spring I8 urges the piston upwardly toraise it substantiallyout of the piston chamber I6c. This pistonchamberI6c,'the bellows chambers 20 and-23, the passagewaysi l and IE9, and theinterior of the cup 26 are allfilled. with hydraulic liquid, such asoilof uniform viscosity even at widely variant temperatures, and extensionof the spring I8 with its attendant movement of the piston I1 merelyresults in free flow of th liquid within the assembly.

The assembly is filled with liquid through the boss 2Ia of the cap 2I,and is purged of all gas bubbles by placing theboss uppermost during thefilling operation. The plug 22 seals the liquid within the assembly. Ifdesired, as shown in Figure .4, the boss 2 Ia and plug 22 can bereplaced with a smal tube 28 brazed into or integral with the cap 2I andprojecting therefrom out of the chamber 23. A Y fitting 29is coupled tothe tube by a hose 30 and has valves 3| in the branches 29a and 2%thereof. One branch 29a is connected to a vacuum pump (not shown). Theother branch-29bis connected to a source of oil (not shown)or-Otherfluid for the tappet.

The bellows I i thus encloses a chamber 20 be- 1 The valve in branch 29ais opened and the other valve in is closed. The pump is then operated toevacuate'the tappet, and, when theair in the tappet is exhausted, theopened valve 3| is closed and the other valve3I opened, whereupon theoil is drawn into the tappet to completely fill all chambers thereofwithout admitting any air. Thetube 28 then has the projecting endthereof pinched closedas at 28a (Fig.5) and a drop of solder 32 isapplied to the tipof the pinched end to seal the tappet.

When-the tappet III-is mounted for operation in the valve train of aninternal combustion engine, for example, as shown in Figure 2, the bodyII-has its cylindrical sidewall IIb slidably mounted in the engine block18- and has its closed bottom IIa acted on by the-engine cam C. Therecess I-Sbof the top cap I9 receives the 5. valve push rod P. With theengine valve (not shown) in closed position,'the valve spring (notshown) exerts some downward pressure on the push rod P which istransmitted through the cap ill to slightly compress the spring [8thereby forcing the piston l1 partly into the piston chamber 160,preferably about half way between the top and bottom of the pistonchamber. Thus, the tappet assumes a somewhat contracted position whenmounted in a valve train even when the valve is completely closed andthe tappetis not transmitting force for opening the .valve. Thiscontracted position is readily assumed from the free expanded positionof Figure 1 by flow of liquid from the chamber 20 through the passageway24 into the chamber 23 whereupon the chamber. 20 partially collapses andthe chamber 23 expands. Liquid that was trapped in the piston chamberI60 can leak from this chamber alongside of the piston 11 into thechamber 20 at a relatively slow rate since the piston IT has a ratherfree sliding fit in the cylinder bore I6b. Back flow of liquid from thechamber I60 through the passageway IBg into the chamber 23 is preventedby the ball 25 which acts as a check valve in seating on the mouth ofthe passageway 16g.

When the cam C rotates in the direction shown by the arrow, the cam lobeC thereon raises the valve body I l and this lifting movement istransmitted to the shell l3 which, in turn, transmits it to the cylinderl6. Liquid trapped in the piston chamber I60 by the ball 25 bottoms thepiston l1 and causes it to rise with the cylinder 16. The piston l Ithrusts against the cap I9 thereby raising the push rod P. During thislifting operation of the valve-opening cycle, some liquid will leakalong the piston I! out of the chamber IBc thereby permitting the pistonto move further into the chamber lBc and creating a clearance in thevalve linkage. This clearance is controlled by the degree of leak-downermitted around the piston and, of course, the degree of leak-down iscontrolled by the relative sizes of th piston and cylinder bore. Forexample only, and not by way of limitation, if the total movement of thepiston I! from its free position at the top of the piston chamber I60shown in Figure l to a completely collapsed position where it isbottomed on the cup 26 is one-eighth of an inch, the tappet, wheninstalled in an engine, has the piston positioned as shown in Figure 2midway between the top and bottom of the piston chamber I60. From thismidposition, the piston can move one-sixteenth of an inch in eitherdirection thereby being capable of adjusting the effective length of thetappet in either direction a distance of one-sixteenth of an inch. Ifthe leak-down during the entire valve-opening cycle of operation causedby movement of the tappet with the lobe C of the cam from the point ofinitial contact with the lobe to the point where the round part of thecam acts on the tappet is .002 inch, there exists a clearance in thelinkage of .002 inch as the cam lobe rotates past the tappet. At thispoint there are three conditions which might exist.

First, if the eifective length of the Valve linkage has remainedconstant during the lift-cycle around the cam lobe, the piston I1 isimmediately biased outwardly .002 inch by the spring l8 and/or bellowsl4 and I5, and the flow of working fluid from the spaced chambers 23 toI60 takes place and the fluid is trapped in piston chamber lBc by thecheck ball 25. Therefore, the

next :lift-cycle begins at substantially zero clearance in the valve.

Secondly, .if, in addition to the leak-down of .002 inch, the effectivelength of the valve linkage has decreased, for example .001 inch, therewill be a clearance of .003 inch in the linkage as the lift-cycle iscompleted. In that case, the piston I1 is biased outwardly .003 inch andthe working fluid will fill the piston chamber I60 so that the nextlift-cycle will again begin with substantially zero clearance.

Thirdly, 'if in addition to the leak-down of .002 inch, the valvelinkage has increased in length, for example .001 inch, a .001 inchclearance would result at the completion of the liftcycleand the pistonI! would only be biased outwardlyfor this distance and a correspondingamount of fluid would be trapped in the piston chamber so that thelift-cycle would begin again with substantially zero clearance.

During overspeeding of an engine, or as a result of faulty cam design,it occasionally happens that the tappet will lose contact with the camface for short periods of time. This is known as cam jumping, and,during the interval of time in which the jump takes place, the tappet isfree to extend itself. If this unwanted extension per lift-cycleisgreater than the leak-down per liftcycle, the valve will eventually beheld off of its seat between lift cycles and thereby result inmalfunctioning of the engine. The tappet of this invention, on the otherhand, minimizes unwanted extension during cam jumping periods byproviding the restricted fluid flow orifice 21, and also by restrictingthe passage l6g so that the rate of fluid flow is choked. This chokingof the working fluid slows down extension of the tappet sufliciently sothat substantially no extension will result in those very short periodsof time when the tappet leaves the cam. By properly calibrating the sizeof the orifice 21 and the flow capacity of the passageway lGg, theunwanted extension of the tappet can be substantially eliminated.

The shell l3 may become heated when the bellows l4 and I5 are weldedthereon, but this heat does not affect the separate cylinder I6 which ispreferably heat-treated for hardness properties. The cylinder [6 can fitrather freely in the shell l3, and may be free to turn therein withoutblocking the passage 24. Likewise, the piston ll floats in the cylinderI5, since it is not anchored to a bellows and only thrusts against thecap l9. This movable relationship of shell, cylinder, and piston,together with parts carried thereby, minimizes galling or scufiingaction on closely mated parts and eliminates torsion strains on thebellows. A

Because the ball check valve coacts with the cylinder and not thepiston, it can be springless and operate efficiently due to fluidpressure differentials alone.

From the above descriptions it will be understood that this inventionprovides a self-contained automatic hydraulic tappet having bellowschambers at opposite ends of a shell surrounding a separatepiston-containing cylinder. The addition of the piston to theself-contained bellows arrangement for carrying all lifting forcesgreatly increases the wear life of the tappet and minimizes danger ofrupturing of any fluid-containing passages.

It will, of course, be understood that various details of constructionmay be varied through a wide range without departing from the prin-'fats-53,756

ciples of .thisinvention and itis, therefora'not the purpose to limitthe patent 'grantedhereon otherwise .than necessitated by the scope ofthe appended claims.

I claimasmy invention:

1. An extensible and contractible device comprising a shell, anopen-ended cylinder in the shell, a check valve in one end of thecylinder controlling flow into the cylinder, a pistonrotatable andslidable in the other end of 'thecylinder, fluid-filled interconnectedexpansible and contractible chamber-defining members secured to oppositeendsof'the shell and communicating with opposite ends of the cylinder, acap secured to one chamber-defining member and acted on by said piston,means biasing the piston outwardlyrof the cylinder against said cap,said pistoni'being freely slidable in said cylinder to accommodaterestricted flow of fluid around the piston whenever the cap loads thepiston and fluid in the cylinder is loaded by the piston and being 'freeto creep with respectto said cylinder in a rotational direction, andmeans connecting the expansible and contractible chambers for transferof fluid therebetween whereby fluid leaking around the loaded piston isfed to one of -said chambers and then transferred to the other of saidchambers forflow through the check valve into the cylinder to bottom thepiston as soon as it is unloaded'and biased outward by the spring.

2. A self-contained hydraulic valve tappet comprising a shell, .anopen-ended cylinder rotatably seatedin said shell, a valve-drivingpiston rotatable and slidable in said cylinder, means for liftingsaidshell and cylinder to load the piston, resiliently eXp-ansiblefluid-filled chamberdeflning means anchored on the ends of the shell andrespectively closing the open ends of the cylinder, a check valveaccommodating fluid flow from one expansible means to the piston andstopping reverse flow of fluid to trap fluid between the cylinder andpiston for driving the valve, said piston being freely fitted in saidmember to accommodate leakage of fluid therearound when said means forlifting loads the piston thereby creating a clearance in the valvelinkage during the valve-lifting cycle and being free to creep withrespect to said cylinder in a rotational direction, and a gapbetween theshell and cylinder defining a conduit for transferring the fluid fromone expansible chamber-defining means to the other irrespective of theangular position of said cylinder relative to said shell for feedingthrough saidcheck valve to the piston as soon as saidmeans for liftingreleases the load on the piston.

3. A clearance-eliminating device comprising a hollow open-ended sheath,a cylinder seated in said sheath, a spring metal bellows welded to theends of said sheath and defining expansible and contractible chamberscommunicating with said cylinder and having end walls spaced outwardlyfrom the cylinder and sheath, a piston slidable in said cylinder andextending into one of said chambers for thrusting against the end wallthereof ,a chest: valve interposed in said cylinder between the other ofsaid chambers and the piston, means interconnecting said chambers forfluid flow, means biasing said piston outwardly of said cylinder againstsaid end wall, said piston being freely slidable insaid member andaccommodating leakage of fluid therearound and being free to creep withrespect to said cylinder in a rotational direction, said cylinder andchambers :for transferring the axial force to said end wall while somefluid leaks around the piston and is transferred back to the check valvefor reintroduction into'the enember upon cessation of the axial force.

4. vA self-contained hydraulic valve tappet comprising a hollowopen-ended shell, spring metal bellows at the ends of said-shelldefining expansible and contractiblechambers, one of said bellows beingclosed by an end cap having a recess adapted to receive :a push rod, theother of said bellows being closed by an end cap having a fluid chargingnipple thereon, a hollow cylinder disposed in said shell andmountedtherein for creeping movement with respect thereto in a rotationaldirection a check valve interposed between the interior of said cylinderand said other of said bellows, a piston freely rotatable and slidablein the cylinder on the discharge side of the check valve, .a springinterposed between the cylinder and piston biasing the piston againstthe end cap for receiving the push rod, and means defining a flow pathbetween the chambers housed by the bellows, said piston being freelyslidable in said cylinder and accommodating a leakage of fluid aroundthe piston during the valve-lift cycle whereupon said fluid istransferred back to the cylinder and trapped beneath the piston by saidcheck valve as soon as the lift-cycle is completed.

5. A self-contained hydraulic valve tappet which comprises a hollowbody, a shell projecting into the body and bottomed thereon, a hollowcylinder seated in the shell and rotatable therein, first and secondfluid-filled bellows each having one end thereof afiixed to the shelland defining chambers communicating with the interior of the cylinder,caps closing the outer ends of the bellows, a piston slidable androtatable in the cylinder and'arranged to'have one end thereof thrustagainst one of said caps and the other end thereof terminate in saidcylinder, a check valve controlling fluid flow between said other end ofthe piston and the adjacent bellows, and a restricted passagewayconnecting the interiors of both bellows whereby fluid trapped betweenthe check valve and the piston will transmit valvelifting force throughthepiston to the end cap actuated thereby while some trapped fluid leaksinto the bellows to be fed on the valve-closing cycle in requiredamounts to the cylinder for maintaining zero clearance.

6. In a self-contained hydraulic valve tappet ofthe'opposed bellows,cylinder and piston type, the improvement of a separate sheathsurrounding thecylinder and sealingly anchoring the inner ends of thebellows, said cylinder and said piston being mounted in said sheath freefrom said bellows, for creeping rotational movement with respectthereto, whereby said cylinder and piston may rotate relative to saidsheath and relative to each other, whereby said cylinder may rotaterelative to said sheath and the piston.

'7. In a self-contained hydraulic valve tappet having a cylinder, apiston slidable and rotatable therein and a bellows defining anexpansible fluid chamber communicating with the cylinder, theimprovements of a shell around the cylinder, a sealing connection fromone end of said shell to one end of the bellows, an end cap, and asealing connection between said end cap and the other end of thebellows, a spring biasing the piston against said end cap and saidpiston and cylinder being free from said bellows, whereby both saidpiston and cylinder may shift rotationally.

8. In a self-contained hydraulic valve tappet having a reciprocablymovable body, a shell mounted in said body for movement therewith, acylinder in said shell, a piston within said cylinder, spring meansurging said piston in an extended position with respect to saidcylinder, an end cap adapted to be engaged by the upper end of saidpiston, a restricted fluid passageway from the lower end of saidcylinder to said piston, a check valve therein, said piston beingmounted in said cylinder with a predetermined clearance, to form arestricted passageway along the walls of said cylinder from the lower tothe upper end thereof, a fluid passageway between said cylinder andshell allowing fluid to pass from one end of said cylinder to the other,the improvements comprising separate bellows closing and formingexpansible chambers at opposite ends of said shell and communicatingwith opposite ends of said cylinders, sealing connections between saidbellows and opposite ends of said shell and a sealing connection betweenone of said bellows and said end cap, said bellows being so constructedand arranged as to be entirely free from said piston and cylinder and topermit rotational creeping movement of said cylinder with respect tosaid shell and rotational creeping movement of said piston with respectto said cylinder.

9. In a self-contained hydraulic valve tappet having a reoiprocablymovable body, a shell mounted in said body for movement therewith andfor rotational creeping movement with respect thereto, a cylinder insaid shell, a piston within said cylinder and a chamber within saidcylinder into which the lower end of said piston moves, spring meansurging said piston in an extended position with respect to said chamber,a restricted fluid passageway into said chamber and a valve in saidpassageway holding fluid under pressure therein, said piston beingmounted in said cylinder with a predetermined amount of clearance toform a restricted passageway allowing a predetermined volume of fluid toleak thereby, a fluid passageway between said shell and cylindercommunicating from one end thereof to the other, expansible bellowsextending from opposite ends of said shell, sealing connections betweensaid bellows and shell, a closure plate sealed to the lower of saidbellows and forming an expansible chamber at the lower end of saidcylinder, and the closure member for the upper of said bellowscomprising an end cap member sealed thereto, free from and adapted to beabutted by the outer end of said piston.

10. In a self-contained hydraulic valve tappet having a reciprocablymovable body, a shell mounted in said body for movement therewith andfor rotational creeping movement with respect thereto, a cylinder insaid shell, a piston within said cylinder and a chamber within saidcylinder into which the lower end of said piston moves, spring meansurging said piston in an extended position with respect to said chamber,a restricted fluid pasageway into said chamber and a valve in saidpassageway holding fluid under pressure therein, said piston beingmounted in said cylinder with a predetermined amount of clearance toform a restricted passageway along the walls of said cylinder allowing apredetermined volume of fluid to leak thereby, a fluid passagewaybetween said shell and cylinder communicating from one end thereof tothe other, expansible bellows extending from opposite ends of saidshell, sealing connections between said bellows and shell, a closureplate sealed to the lower of said bellows and with said bellows formingan expansible chamber extending from the lower end of said cylinder, andthe closure member for the upper of said bellows comprising an end capmember sealed thereto and free from and adapted to be abutted by theouter end of said piston, said end cap member affording a means foractuating a push rod of the valve opening mechanism and being soconstructed and arranged as to be engaged with said piston and permitcreeping movement of said piston with respect to said cylinder and endcap in a rotational direction.

HERBERT H. ENGEMANN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,098,115 Voorhies Nov. 2, 19372,109,459 Best Mar. 1, 1938 2,109,899 Van Ranst Mar. 1, 1938 2,278,963Arola Apr. 7, 1942 2,325,932 Banker Aug. 3, 1943 2,376,182 Peterson, Jr.May 15, 1945

